1. Technical Field
The present invention relates to printed circuit boards, and particularly to insulating films for printed circuit boards, printed circuit board substrate made form the insulating films and printed circuit boards made from the printed circuit board substrates.
2. Discussion of Related Art
Recently, to meet increasingly strict requirement of electronic devices, printed circuit boards are becoming greater in number of layers and higher in circuit distribution density. Accordingly, electromagnetic interference (EMI) between different parts of printed circuit boards is correspondingly increased, which greatly decreases performance of printed circuit boards.
Currently, to reduce EMI in printed circuit boards, additional electromagnetic shielding layers (i.e. a copper layer without circuit formed therein) may be employed in printed circuit boards. However, these additional electromagnetic shielding layers increase thickness and decrease a circuit density of printed circuit boards. Therefore, what is needed is a new printed circuit board capable of providing electromagnetic shielding ability without employing additional electromagnetic shielding layers.